﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

#if !NULLABLE_ATTRIBUTES
namespace System.Diagnostics.CodeAnalysis;

///// <summary>Specifies that null is allowed as an input even if the corresponding type disallows it.</summary>
//[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
//internal sealed class AllowNullAttribute : Attribute
//{ }

///// <summary>Specifies that null is disallowed as an input even if the corresponding type allows it.</summary>
//[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
//internal sealed class DisallowNullAttribute : Attribute
//{ }

///// <summary>Specifies that an output may be null even if the corresponding type disallows it.</summary>
//[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
//internal sealed class MaybeNullAttribute : Attribute
//{ }

///// <summary>Specifies that an output will not be null even if the corresponding type allows it.</summary>
//[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
//internal sealed class NotNullAttribute : Attribute
//{ }

///// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter may be null even if the corresponding type disallows it.</summary>
//[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
//internal sealed class MaybeNullWhenAttribute : Attribute
//{
//    /// <summary>Initializes the attribute with the specified return value condition.</summary>
//    /// <param name="returnValue">
//    /// The return value condition. If the method returns this value, the associated parameter may be null.
//    /// </param>
//    public MaybeNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;

//    /// <summary>Gets the return value condition.</summary>
//    public bool ReturnValue { get; }
//}

/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter will not be null even if the corresponding type allows it.</summary>
[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
internal sealed class NotNullWhenAttribute : Attribute
{
    /// <summary>Initializes the attribute with the specified return value condition.</summary>
    /// <param name="returnValue">
    /// The return value condition. If the method returns this value, the associated parameter will not be null.
    /// </param>
    public NotNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;

    /// <summary>Gets the return value condition.</summary>
    public bool ReturnValue { get; }
}

/// <summary>Specifies that the output will be non-null if the named parameter is non-null.</summary>
[AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, AllowMultiple = true, Inherited = false)]
internal sealed class NotNullIfNotNullAttribute : Attribute
{
    /// <summary>Initializes the attribute with the associated parameter name.</summary>
    /// <param name="parameterName">
    /// The associated parameter name.  The output will be non-null if the argument to the parameter specified is non-null.
    /// </param>
    public NotNullIfNotNullAttribute(string parameterName) => ParameterName = parameterName;

    /// <summary>Gets the associated parameter name.</summary>
    public string ParameterName { get; }
}

///// <summary>Applied to a method that will never return under any circumstance.</summary>
//[AttributeUsage(AttributeTargets.Method, Inherited = false)]
//internal sealed class DoesNotReturnAttribute : Attribute
//{ }

///// <summary>Specifies that the method will not return if the associated Boolean parameter is passed the specified value.</summary>
//[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
//internal sealed class DoesNotReturnIfAttribute : Attribute
//{
//    /// <summary>Initializes the attribute with the specified parameter value.</summary>
//    /// <param name="parameterValue">
//    /// The condition parameter value. Code after the method will be considered unreachable by diagnostics if the argument to
//    /// the associated parameter matches this value.
//    /// </param>
//    public DoesNotReturnIfAttribute(bool parameterValue) => ParameterValue = parameterValue;

//    /// <summary>Gets the condition parameter value.</summary>
//    public bool ParameterValue { get; }
//}
#endif